Water wells are commonly used for providing domestic water in rural areas and in some suburban areas. Such wells are commonly constructed by drilling, boring, or otherwise excavating a hole into the ground from the surface into a water-bearing stratum or aquifer. To prevent collapse of the hole, a generally tubular casing is inserted through the hole into the aquifer. This casing extends from the aquifer to above grade level, where the casing terminates and is typically covered by a sanitary well cap.
The casing will typically have an opening in it called a pitless well adapter for connection of piping for removal of the water. This opening is commonly placed below grade level, below the frost line, to prevent freezing of pipes attached to the opening in the casing. A pump or other means for extracting the water from the aquifer and raising it to the level of the opening in the casing is commonly attached at or near the upper terminus of the well casing, usually to the well casing itself.
Water found near the surface of soil, and indeed rain water itself, may contain significant contaminants. Furthermore, surface water will readily seep downwardly, or channel, immediately adjacent to the well casing. If contaminated surface water is allowed to contact the outside of the casing before it has percolated through several feet of soil to filter and purify the water through the action of bacteria, contaminated water can readily channel down adjacent to the casing and enter the aquifer, causing pollution.
To prevent this, cased water wells typically include a concrete pad surrounding the casing, and extending a substantial distance in all directions from the casing. This concrete pad has an upper surface which is sloped away from the casing so that rain water, dirt, oils from the pump or other contaminants will be drained away from the well casing to the outer edge of the concrete pad. Thus, surface water drained off the pad must percolate through several feet of soil before coming in contact with the outside of the casing.
The installation of this concrete pad is costly from the standpoint of time and material. Installing the concrete pad requires extra excavation of the soil around the upper portion of the well casing and a form for pouring the concrete.
The concrete pad must be free from cracks and the outside of the casing where it contacts the concrete must be sealed with a mastic or other sealant to prevent water from seeping through the concrete pad adjacent the outside of the casing at the point of entry of the casing. If the concrete pad is formed too soon after excavation of the soil around the casing, subsequent ground settling can cause cracking of the concrete which would defeat the purpose of the pad. Such ground settling can also cause rupturing of the mastic seal around the well casing, similarly defeating the purpose of the concrete pad. Furthermore, dirt can accumulate around the well casing at the point of entry through the concrete pad, contributing to weed and grass growth which, in turn, contributes to channeling of water through this point of entry down the outside of the casing.
The concrete pad may be installed either at or near grade level or below grade level, below the pitless well adapter. When installed at or near grade level, inspection or repair of the pitless adapter below the concrete pad requires a great deal of excavation below the pad which, in turn, subjects the concrete pad to the potential for cracking and rupture of the mastic seal. Furthermore, inspection and excavation under the concrete pad can be very dangerous to personnel. Installation of the concrete pad below the pitless well adapter to minimize these problems requires much more excavation and resultant expense. In either case, concrete can only be installed within a certain range of temperatures, which prevents the installation of wells during times of the year when temperatures are too cold.